I have around $5000 net rental income, but turbotax automatically set me around $16,000 depreciation. I don't need that much, how to change it to a lower number?

No. It is based on the value of your home. If you have so little income, is it because it was not rented all year or because you are renting at below Fair Rental Income? If this is an Not For Profit, you should not include it on Schedule E, but rather as other income on the 1040.